mechanical ventilation

Question 1

mechanical ventilation define

Answer 1

gas driven into airways under a positive pressure which allows inflation of the alveoli and movement of gas from mouth to alveoli

Question 2

mechanical vs normal always

Answer 2

higher force required than for normal ventilation
positive pressure breathing
smaller tube ETT than trachea which increases resistance to airflow + pressures requires to deliver adequate tidal volumes
sputum clearance
loss of normal humidification and impairment in movement of secretions

Question 3

indications for ventilatory support

Answer 3

respiratory failure 
support for other failing organs 
support for mechanical dysfunction 
during use of high levels of sedation and anaesthesia 
To decrease ICP

Question 4

potential complications

Answer 4

tracheal injury 
CV compromise 
changes in rest system 
barotrauma 
increased infection risk 
psychological

Question 5

mechanical ventilation assessment

Answer 5

mode of vent 
FiO2 = flow of inspired oxygen 
PEEP - positive end expiratory pressure 
I:E ratio - inspiration to exp ratio 
RR= respiratory rate 
TV - tidal volume 
pMAX - peak maximal pressure in lungs 
PS pressure support

Question 6

modes of ventilation

Answer 6

mandatory / machine breaths
patient / spontaneous breaths
combination of mandatory and spontaneous

Question 7

mandatory / machine breaths

Answer 7

generated by machine 
no active input from pt 
no muscular activity 
if pt doesn't / can't breathe: no problem 
pressure control PC
volume control VC

Question 8

patient / spontaneous breaths

Answer 8

patient driven
some support given by ventilator
if patient does not initiate breath, no breath will take place
muscular activity
modes: PS pressure support
Volume support
CPAP - continuous positive airway pressure

Question 9

patient / spontaneous breaths

support ventilation

Answer 9

advantages
- patient controls rate, volume and duration of breaths
patient comfort
may decrease WOB

disadvantages
- may not be enough ventilatory support if patient condition changes / if there are changes in compliance / resistance
patient must be able to trigger a breath

Question 10

patient spontaneous breaths

CPAP

Answer 10

continuous positive airway pressure Application of constant positive pressure throughout the spontaneous ventilatory cycle
No mechanical inspiratory assistance is provided
Requires active spontaneous respiratory drive
Same physiologic effects as PEEP
TV and RR determined by patient
Often final form of support before extubation

Question 11

flow of oxygen

Answer 11

expressed as %

Question 12

positive end expiratory pressure

Answer 12

Pressure in lungs at end expiration
Compensate for increased dead space 
<5cmH2O only in hyperinflated conditions
5cmH2O normal
Increasing Peep is an attempt to increase open lung units, improve gas exchange and reduce WOB
>10cmH2O unable to disconnect vent

Question 13

inspiratory to exp ratio

Answer 13

Normally 1:2-3
Lengthening Inspiration 1:1 or 2:1 improves oxygenation
Lengthening expiration 1:3-4 decreases gas trapping

Question 14

RR - respiratory rate

Answer 14

Normal 12-16 breaths per min
<12 due to decreased level of arousal, decreased respiratory drive, CNS depression
> 20 anxiety, sepsis, increased resp drive, resp failure
As a vent strategy to improve gas transport

Question 15

TV - tidal volume

Answer 15

dependent on height, sex, and age
range 450-600ml
6-8ml per kg of body weight

Question 16

weaning from MV

Answer 16

Manipulation of settings to gradually reduce support from machine
Rehabilitation of patient to improve respiratory, trunk and limb muscle strength
Resolution of indication for ventilation
Different methods, times and principles
Tracheostomy can be used for prolonged mechanical ventilation and as a weaning method
Understanding of why the patient was initially ventilated is key to guidance of weaning

Question 17

role of physiotherapy

Answer 17

Prevent and treat atelectasis
Aid sputum clearance
Rehab 
Weaning from mechanical ventilation
Prevention of secondary complications
Thorough understanding of impact of mechanical ventilation on other systems